K. M. Biswas

Cassiadinine, a chromone alkaloid and (+)-6-hydroxy-mellein, a dihydroisocoumarin from Cassia siamea

Abstract Cassiadinine, a new chromone alkaloid and (+)-6-hydroxymellein, a new dihydroisocoumarin isomer have been isolated together with three triterpenoids, cycloart-23-en-3β,25-diol, friedelin and betulin, a chromone derivative, 5-acetonyl-7-hydroxy-2-methylchromone and γ-sitosterol from the petrol and chloroform extracts of the flowers of Cassia siamea .

Diborane as a reducing agent - VI the novel reduction of indole-1-carboxaldehydes to 1-methyl- indoles, di(indolyimethyl) ethers and indolylmethyl indolines☆

Abstract Reduction of the indole-1-carboxaldehydes ( 1a - 1f ) with borane /THF gives the 1-methylindoles ( 4 ) in 42-91-% yields together with the di(indolylmethyl)ethers ( 8 ), the indolyl-methyl indolines ( 7 ), the unsymmetric ether( 10 ) and the indolenine ( 11 ) as the minor products, except 7a . This appears to be the first report on the formation of symmetric ethers in the borane/THF reduction of an oxygen function. The formation of 7a and 7b from 1a and 1b implies that electrophilic substitution takes place primarily at position 3 of 3-substituted indoles, 1c - 1f did not form the corresponding 7 probably because of steric hindrance. These results are discussed in relation to the mechanisms of borane/THF reduction, origin of the different products and electrophilic substitution in 3-substituted indoles.

Nuclear magnetic resonance VI. Some quantitative applications of carbon-13 NMR spectroscopy to phenylindoles

SummaryThe number of carbons represented by each signal of the phenylindoles1,4, and5 is measured quantitatively by integration of their13C NMR spectra, recorded after adding chromium(III) acetylacetonate to the sample solutions as a paramagnetic relaxation agent. Their carbon chemical shifts are assigned unambiguously; the literature assignments of4 are confirmed. By a comparative study of the carbon chemical shifts of1,4, and5, those of2 and3 are also assigned. Theortho carbons of the phenyl group of4 resonate upfield with respect to thepara carbon. Theortho carbons of the 2- and 3-phenyl moieties of1–3 and5, however, are found to absorb downfield from the correspondingpara carbons, probably because of steric and/or electronic effects exerted by their neighbouring phenyl group.ZusammenfassungDie Anzahl der durch jedes Signal der Phenylindole1,4 und5 repräsentierten Kohlenstoffatome wird durch Integration der nach Zusatz von Chrom(III)acetonylacetat als Relaxationsreagens aufgenommenen13C-NMR-Spektren bestimmt. Ihre chemischen Verschiebungen werden eindeutig zugeordnet; die Literaturwerte für4 werden bestätigt. Durch eine vergleichende Untersuchung der13C-chemischen Verschiebungen von1,4 und5 können jene von2 und3 ebenfalls zugeordnet werden. Dieortho-Kohlenstoffe der Phenylgruppe von4 sind gegenüber denpara-Kohlenstoffatomen zu höherem Feld verschoben. Für die 2- und 3-Phenyl-Substituenten von1–3 und5 kehren sich die Verhältnisse um, wahrscheinlich wegen sterischer und/oder elektronischer Effekte der benachbarten Phenylgruppe.

SYNTHESIS OF A TRIFLUOROMETHYLINDOLOCARBAZOLE, NOVEL CYCLIC 27- AND 36-MEMBERED N-BENZYLTRI-AND-TETRAINDOLES, AND AN N-BENZYLTETRAINDOLYLTRIMETHANE

Summary. 5,11-Dihydro-5,11-dibenzyl-6-trifluoromethylindolo[3,2-b]carbazole (6) and the cyclic N-benzylindole trimer 4 were synthesized from both N-benzylindole-3-methanol (1) and N,N′-dibenzyl-3,3′-diindolylmethane (2) by treatment with trifluoroacetic anhydride. The former also gave the 36-membered cyclic N-benzylindole tetramer 7, and the latter furnished N-benzyl-3-trifluoroacetylindole (8). Heating 1 in aqueous methanol also yielded the trimer 4 along with 2, the N-benzylitriindolyldimethane 3, and the N-benzyltetraindolyltrimethane 5 whose structure and solid-state conformation were determined by X-ray crystallographic analysis. The results are discussed and plausible mechanisms of the reactions leading to 3–8 are presented.Zusammenfassung. 5,11-Dihydro-5,11-dibenzyl-6-trifluormethylindolo[3,2-b]carbazol (6) und das cyclische N-Benzylindoltrimer 4 wurden aus N-Benzylindol-3-methanol (1) und N,N′-Dibenzyl-3,3′-diindolylmethan (2) durch Behandeln mit Trifluoracetanhydrid synthetisiert. Ersteres ergab auch das36-gliedrige cyclische N-Benzylindoltetramer 7, letzteres N-Benzyl-3-trifluoracetylindol (8). Erhitzen von 1 in wässrigem Methanol führte zum Trimer 4– zusammen mit 2, dem N-Benzyltriindolylmethan 3 und dem N-Benzyl-tetraindolyltrimethan 5, für welches Struktur und Konformation imfesten Zustand durch Röntgenstrukturanalyse abgeleitet wurden. Die Resultate werden diskutiert, und plausible Mechanismen für die Reaktionen, die zu den Verbindungen 3–8 führen, werden vorgestellt.

Diborane as a reducing agent IX: Reduction of aTris(trifluoroacetyl)enaminospiroindoline

SummaryReduction of the title compound (2) with diborane furnishes 1-trifluoroethyl-3-(2′-(trifluoroethylamino)ethyl)-3-vinylindoline (4), 1-hydroxy-trifluoroethyl-3-(2′-(trifluoroethylamino)ethyl)indole (5), and 1-methyl-2-trifluoroethyl-1,2,3,4-tetrahydro-β-carboline (6). However, treatment of2 with lithium aluminum hydride, H2/Pd on charcoal, and sodium borohydride affords hydroxyspiroindolenine8, hydroxy-bis(trifluoroacetyl)enaminospiroindoline9, andN-ethyltryptamine7, respectively. The results are discussed and the mechanisms of the reactions leading to4–8 are presented.ZusammenfassungReduktion der Titelverbindung (2) mit Diboran ergibt 1-Trifluoroethyl-3-(2′-(trifluoroethylamino)ethyl)-3-vinylindolin (4), 1-Hydroxy-trifluoroethyl-3-(2′-(trifluoroethylamino)ethyl)indol (5) und 1-Methyl-2-trifluoroethyl-1,2,3,4-tetrahydro-β-carbolin (6). Behandlung von2 mit Lithiumaluminiumhydrid, H2/Pd auf Aktivkohle und Natriumborhydrid führt jedoch zu Hydroxyspiroindolenin8, Hydroxy-bis(trifluoroacetyl)enaminospiroindolin9 und N-Ethyltryptamin (7). Die Ergebnisse werden diskutiert und die Mechanismen der zu den Produkten4–8 führenden Reaktionen werden vorgestellt.